#include <iostream>
#include <string>
#include <sstream>

using std::cout;
using std::endl;
using std::string;
using std::cin;
using std::istringstream;

int main(void) 
{
    cout << "开始" << endl;
    string line;
begin:
    std::getline(cin, line, '\n');
    int point = 0;
    int flag = 0;
    for (auto &ch : line){
        if(flag == 0){
            if(ch == '-'){continue;}
        }
        flag++;
        if (ch == '.'){++point;}
        if ((isdigit(ch) != true && ch != '.') || point > 1){
            cout << "错了哦" << endl;
            goto begin;
        }
    }

    istringstream iss(line);
    double num;
    iss >> num;
    cout << num << "\n结束" << endl;

    return 0;
}